EnergyPlus Training FAQ

When we announced our plan to run an EnergyPlus training (for both architects and engineers), we also launched a survey to gauge the interest of the people in the region. We have also received feedbacks on our plan. We have answered the questions directly to the person, but we think it will be useful for everyone to know what other people are thinking. The summary is presented in the form of question-and-answer below.

About the Workshop?

Question: What is the aim of this workshop?

Answer: To equip designers with the technical skills to be able to perform building simulation using Energy Plus and understand how to use the tool as part of the Integrated Design Process.

Question: Can we do modelling for LEED after this workshop?

Answer: You are missing the point. This workshop will show you that energy modelling is much more than LEED compliance. But this workshop will NOT train you specifically on how to do modelling for LEED. That is not the focus of this workshop. However, we do have some sessions to discuss LEED modeling requirements. With the materials in this workshop, the participants will be well equipped to do modeling for LEED, although there will be a lot of things that they need to learn on LEED requirements that is not covered in this workshop.

Question: Why do you target architects for this workshop? Do you expect them to do energy modeling?

Answer: There are two levels of target that we aim in training the architect. The first one is to get the architects to understand the big picture of doing simulation so that they can better communicate their ideas with the engineers. The second one is yes, we do expect them to do energy modeling. A lot of architects have been doing this. Of course they will need to be well conversant in HVAC system to do a full blown LEED modeling, for example. But what we are trying to promote to architects is to do the load analysis, which can be done without even specifiying a single piece of HVAC equipment.

Question: Can an architect register for Day 3 (HVAC system)?

Answer: Yes, they can. What we will learn in Day 3 is how to model the system, with the assumption that the participants know how the system work. There will be a brief explanation on each system used in the sessions, and this can be a great learning opportunity for architects to learn about them. However, the general rule applies: do not expect to be able to do HVAC systems modelling if you do not know how it works in real life.

Question: Is there a pre-requisite for this workshop?


  • Day 1: practically no pre-requisite, other than the general use of computer, e.g. file manipulation (copying, moving, deleting, etc), working with spreadsheet (sorting, using formula, using function, creating a graph, etc).
  • Day 2: you need to know how to develop and edit EnergyPlus input file (with or without OpenStudio), run EnergyPlus and analyze results.
  • Day 3: as Day 2, plus general understanding of HVAC systems. Having specific knowledge on the HVAC systems discussed in the sessions is not mandatory, but there will be no detailed explanation on them either.

Question: What do we need to prepare for the workshop?

Answer: The participants need to have their own laptop computer to attend the workshop. EnergyPlus and OpenStudio work on Windows and Mac, however only Windows will be supported during the workshop. There are a number of programs that need to be installed before the workshop. The details will be emailed to all participants at a later date.

Question: Why the cost for this workshop is so expensive?

Answer: Nope, the cost for this workshop is not expensive. Please look around and you will agree that this workshop is not expensive.

Question: Why the cost for this workshop is so cheap?

Answer: IDL has the mission to promote the use of energy simulation to building designers in our region, especially in Boise area. Based on our survey, the fee that we set is more or less the price for which local folks are willing to invest in something so "geeky" and yet not so "flashy" (for example, compared to some of the 3D visual programs, which can easily charge more and people will still want to invest in it). If the local folks are willing to invest this much, then we have met our target. If along the way, people from other regions benefit from the cheap cost, then good for them. Note that the registration for this workshop is on a first-come first-serve basis, regardless of where you live. We reserve the right to cancel the whole workshop if the minimum number of participants is not met (with a full refund), and to close the registration once the maximum number of participants is reached.

Question: Will there be any take-home materials given to the students of the seminar? Anything that will allow them to use this new-found knowledge in a practical way?

Answer: Almost all the materials to learn EnergyPlus is available online. There are two main points that the participants will learn from this workshop: (1) how to use the information to solve their problem when they are doing simulation (2) how to use the information to learn more. The participants will have all the presentations and exercises in the CD. The material will also include "homework problems" that they can work on after the workshop.

Question: Will the hands-on portions of the sessions include "realistic" buildings and carry through as much as possible for continuity?

Answer: Yes, all the buildings are realistic. This includes the cases where we need to focus on a single zone (basically a box), where we will take out one zone from real building. But the cases will not neccessarily carry through throughout the workshop.

Question: Any chance that the workshop will be streamed (via webcast) for those of us in the faraway east?

Answer: No.

About EnergyPlus?

Question: What is EnergyPlus?

Answer: From"EnergyPlus is a whole building energy simulation program that engineers, architects, and researchers use to model energy and water use in buildings. Modeling the performance of a building with EnergyPlus enables building professionals to optimize the building design to use less energy and water".

From "Getting Started" document of EnergyPlus: "EnergyPlus has its roots in both the BLAST and DOE–2 programs. BLAST (Building Loads Analysis and System Thermodynamics) and DOE–2 were both developed and released in the late 1970s and early 1980s as energy and load simulation tools. Their intended audience is a design engineer or architect that wishes to size appropriate HVAC equipment, develop retrofit studies for life cycling cost analyses, optimize energy performance, etc. Born out of concerns driven by the energy crisis of the early 1970s and recognition that building energy consumption is a major component of the American energy usage statistics, the two programs attempted to solve the same problem from two slightly different perspectives. Both programs had their merits and shortcomings, their supporters and detractors, and solid user bases both nationally and internationally."

Question: From "Getting Started" document of EnergyPlus: "Why does EnergyPlus exist and what were its original goals?"

Answer: From "Getting Started" document of EnergyPlus: "The existence of EnergyPlus is directly related to some of the increasingly obvious shortcomings of its predecessor programs—BLAST and DOE–2. Both programs, though still valid tools that will continue to have utility in various environments, have begun to show their age in a variety of ways. Both BLAST and DOE–2 were written in older version of FORTRAN and used features that will eventually be obsolete in new compilers. Both programs consisted of a significant amount of “spaghetti code” and outdated structures that made it difficult to maintain, support, and enhance. Neither BLAST nor DOE–2 is able to correctly handle feedback from the HVAC system to the zone conditions. Finally, the speed with which new technology in the HVAC field is developed has far outpaced the ability of the support and development groups of both programs to keep the programs current and viable. This is really the key issue in the existence of EnergyPlus: there simply are not enough researchers worldwide who have enough experience with the complex code of the programs to keep pace with new technology. In addition, due to the years of experience necessary to make modifications to either BLAST or DOE–2, it is extremely expensive and time consuming to produce models or train someone to become proficient in either program’s code.".

Question: What EnergyPlus is NOT?

Answer: From "Getting Started" document of EnergyPlus:

  • EnergyPlus is not a user interface. It is intended to be the simulation engine around which a third-party interface can be wrapped. Inputs and outputs are simple ASCII text that is decipherable but best left to a GUI (graphical user interface). This approach allows interface designers to do what they do best—produce quality tools specifically targeted toward individual markets and concerns. The availability of EnergyPlus frees up resources previously devoted to algorithm production and allows them to be redirected interface feature development in order to keep pace with the demands and expectations of building professionals.
  • EnergyPlus is currently not a life cycle cost analysis tool. It produces results that can then be fed into an LCC program. In general, calculations of this nature are better left to smaller “utility” programs which can respond more quickly to changes in escalation rates and changes to methodologies as prescribed by state, federal, and defense agencies.
  • EnergyPlus is not an architect or design engineer replacement. It does not check input,
    verify the acceptability or range of various parameters (expect for a limited number of very basic checks), or attempt to interpret the results. While many GUI programs assist the user in fine-tuning and correcting input mistakes, EnergyPlus still operates under the “garbage in, garbage out” standard. Engineers and architects will always be a vital part of the design and thermal engineering process.

Question: Is it true that EnergyPlus does not have an interface?

Answer: Technically that is not true. The accurate statement is that EnergyPlus is developed as engine-only. The development of the interfaces is intentionally left to the third-party developers. There are a number of programs that can be used as an interface to EnergyPlus. Programs like DesignBuilder fully "wraps" EnergyPlus around, where you do not even realize that it is calling EnergyPlus when it runs.

Question: What is OpenStudio?

Answer: From"OpenStudio is a SketchUp Plug-in that allows you to use the standard SketchUp tools to create and edit EnergyPlus zones and surfaces. You can explore your EnergyPlus input files by using all of the native SketchUp 3D capabilities to view the geometry from any vantage point, apply different rendering styles, and perform shadowing studies. The plug-in allows you to mix EnergyPlus simulation content with decorative content such as background images, landscaping, people, and architectural finish details—all within the same SketchUp model".

We will use OpenStudio in this workshop.

Question: How does OpenStudio work with EnergyPlus

Answer: From"OpenStudio Plug-in automatically generates the input for an EnergyPlus object when the user draws a surface in SketchUp. OpenStudio Plug-in then enables users to launch EnergyPlus simulations and view the results without leaving SketchUp. Additionally, OpenStudio Plug-in will generate a design in SketchUp based on EnergyPlus input files".

Question: How is EnergyPlus compared to other programs?

Answer: Please read the following paper. Note that the EnergyPlus capabilities described in this paper is as of 2005, which was way outdated.

Drury B Crawley, Jon W Hand, Michael Kummert, Brent T Griffith. 2005. "Contrasting the Capabilities of Building Energy Performance Simulation Programs. Downloadable from this link.

Why EnergyPlus?

Question: I’ve asked many people around here about whether we should hold an EnergyPlus training and the answer I keep getting back is “NO” until there is a workable interface. Why do you decide to do the EnergyPlus workshop?

Answer: What is a "workable" interface? Is eQuest a workable interface? Or is Ecotect workable? In terms of geometry development, SketchUp is much more workable than eQuest. Yes, OpenStudio is very limited in terms of HVAC interface. But then you do not want architect to mess around with complex HVAC systems. So, OpenStudion is workable interface for architect. Of course we cannot wait for the magic button, i.e. one BIM model that can spit out all analysis. There will be no workable solution if we are waiting for this button.

Question: I’ve read and been told that the SketchUp interface makes EnergyPlus easier to use for experienced users who understand the program in depth, but that for beginners and/or inexperienced users it just makes it a whole lot easier to make big mistakes.

Answer:Firstly, the characterization of OpenStudion in the above question is not accurate, and very subjective. Secondly, it is much better to make mistakes -- meaning, wrong input -- in EnergyPlus, because for sure it will not run. Instead, it will stop and give the exact error messages. Other programs, like eQuest, will (almost) always run even if your input is much less than perfect. Be it eQuest or EnergyPlus, we should not let anybody design building with it without some kind of in-depth understanding of the program.

Question: A few of the big engineering firms tell me they used EnergyPlus in a limited way, but are still MUCH more likely to use eQuest. I’d love to hear what has led you to think you can get an architect to learn EnergyPlus when most engineers tell me they still don’t use it because of the lack of a good interface.

Answer:We should not compare what engineers need with what architects need. If an engineer wants eQuest more than EnergyPlus, the interface they are talking about is the interface for HVAC. Exactly the interface that we want architects to stay away from. IDL wants to promote load analysis for architects. And for this we only need the ideal HVAC system, which can be handled within OpenStudio. Only DOE2 (and its derivatives) requires a complete HVAC system to run. EnergyPlus has released itself from that requirement. Other simulation program (like ESP-r, that is popular in Europe) runs by default without any explicit HVAC system. So when we talk about interface, we are talking about different requirements between architects and engineers.

Having said all that, this is a very valid concern. We are prepared to re-calibrate our confidence in this matter. We speak from our own experience in training architecture students at the IDL. All of them are architecture students and have zero experience in EnergyPlus. Of course they have a very intense exposure, but then again it is not beyond reasonable assumption that any architect can also do it.

We also need to re-calibrate the expectation of the architects. We need to spell out that architect should not do simulation for LEED unless they are fully conversant with the complexity of HVAC systems. What we want is for the architect to be able to do load analysis on the projects they are working on.

Question: Does the EnergyPlus program now have input and output devices that would be easy for your average engineer/designer/architect to utilize, if they are not a computer programmer?

Answer:This is a question that needs to be addressed in multiple questions and answers below.

Question: Is EnergyPlus only for computer programmer?

Answer:No, you do not have to be a computer programmer to use EnergyPlus. If by "computer programming" you mean that we write the code in Fortran and compile it, the answer is no. I am trying to understand where this term "computer programmer" came from? Does editting the input file in text mode count as computer programming? If editting the input file in text mode count as computer programming, then the answer is yes. But this is no strange requirements. I expect my EnergyPlus modeller to be fully conversant in the terms of the IDF file, just as I expect my DOE2 modeller to be conversant with the terms in INP file. Editting an input file in text mode is no computer programming. It is understanding your input.

Question: Do you have to edit the input file in text mode to use EnergyPlus?
Answer: That depends on the problem you are trying to answer. More specifically, that depends on the HVAC system that you use for the project.

EnergyPlus has OpenStudio as the geometry modeller. It is a SketchUp plugin, so the geometry development and manipulation will be handled in SketchUp. If you compare it with eQuest, Sketch-Up is much more easier to use to develop your geometry.
We used to export the geometry from OpenStudio and add the HVAC system in text mode. However, since EPlus v5, OpenStudio has the capability to add an ideal HVAC system that is useful for load analysis. You can even run the simulation from within OpenStudio and import the result back to it. EPlus has just release v6. I do not yet know what are the new features they have in this area. I would expect they will include another type of HVAC system.

Typically you need to open the input file in text mode if you need to use other kinds of HVAC system. For example, package single zone, or VAV, or whatever else you want. Usually, what this means is that you cut-and-paste one HVAC template object to the input file, and edit the input according to your setting. This process is NOT computer programming. I have our architecture students do this all the time, so I expect any architect and engineer -- that is capable of typing in Notepad -- can do it as well.

Question: What does text editting mean?

Answer: Text editting means opening the input file (the IDF file) in a text editor (e.g. Notepad in Windows). From time to time, you need to do this for a number of reasons, from the simple reasons to the more complex ones. The simple reason can be it is much faster to change one number in the IDF file in Notepad, compared to opening the file in SketchUp. The most complex reason is to develop the HVAC systems manually, where you will literally connect the equipments node by node.

Question: Is it easy to use EnergyPlus?

Answer: The word "easy" should not be used to characterize the simulation process. Its not rocket scince, sure. But it is never easy. Whatever your simulation program is. If you want to do building performance simulation, you should at least well versed in heat transfer, at least at the high school physics level. We can hide the numerical parameters entirely (for example the difference between transfer function method and finite difference method, etc), but not the physical parameters.

Question: If you are familiar with eQUEST, could you tell me why, in your opinion, (where we have already spent considerable money training our staff to use eQUEST), EnergyPlus would be better to use than eQUEST? What are the advantages and the disadvantages comparing EnergyPlus and eQUEST?

Answer: We choose not to answer the questions, other than to point out that EnergyPlus is supported by the US-DOE. While many people think this is not important, this is not a small feat. With this support EnergyPlus can have a six-months release cycle (April and October), each release comes with a bunch of new features.

Another important point to highlight, and this point applies regardless whatever tools you use, is that you should use simulation tools to promote integrated design as opposed to compliance, including LEED compliance. Engineers should help the architect since very early stage of the project. IDL always promotes multi-domain multi-tool simulation, which means (1) energy is only one performance parameter and (2) the design tool should evolve from the simplest form of tool, i.e charts and tables first before more complex tools.

The point is: there is no "better" tool. In a competitive world, you should better be equipped with ability to solve the problems with the best tool for the problem. Investing in a single computer program is not a good policy. What is important for firms is the bottomline: the number of hours to do a complete simulation from scratch to a final report. What we found based on our own experimentation, there is no significant difference in whatever programs you use. In the end it is a matter of:

  • preference: do you want to click or do you want to edit the text file? Do you want to have a program that will always run or a program that will stop running unless you have a good input?
  • capabilities: is your program capable of modelling the problem at hand?